“Scotland”, declared a young Alex Salmond in May 1975, “knows from bitter experience what treatment is in store for a powerless region of a common market.”

I discovered that quote while researching a biography of the former first minister and was struck by the contrast with his stance on the European Union a few decades later. Politicians, of course, are allowed to change their minds, but Salmond’s represented quite a journey.

His youthful disdain for the European project also opens a fascinating chapter on Scotland in historian Robert Saunders’ new book on the UK’s 1975 Common Market referendum, “Yes to Europe!” (Cambridge University Press). It also provides a fascinating insight into Scottish politics of that era.

In early 1975, the fear was that Scotland would vote “No”, with anti-Market opinion led by the then buoyant SNP. Unionists were concerned that a differential vote – ie England voting “Yes” and Scotland “No” – would unravel the United Kingdom. Indeed, a February poll for the (then) Glasgow Herald found that only 29 per cent of Scots favoured continuing membership while 45 per cent wanted to leave.

A majority of Scottish MPs had also rejected Harold Wilson’s “renegotiated terms” in the House of Commons, thus the SNP sought to lead the “Get Scotland Out” campaign. And given votes were to be counted regionally, it hoped for a differential outcome (as in June 2016, just the other way around). Yet the referendum also exposed divisions within Scottish Nationalism.

Officially, the SNP position was to reject membership “on London’s terms”, although its campaigning rhetoric also suggested hostility to membership in principle. Nationalists had once been quite keen on European unity, but in the 1960s this cooled as the UK parties became more enthusiastic. Partly this was the SNP’s long-standing compulsion to define itself against its opponents, but there was something else too.

For a party dedicated to regaining Scotland’s “sovereignty”, there were obvious problems in championing a Common Market which diluted that sovereignty, however modestly. Today, Nicola Sturgeon rejects any comparison between the two unions (British and European), but in the 1970s Salmond et al drew equivalence. Billy Wolfe even argued that plans for monetary and customs union looked suspiciously like the UK on a continental scale.

Nevertheless, a significant minority of Scottish Nationalists remained pro-European, which resulted in what Gordon Wilson later called a “flimsily clad” compromise, with policy documents pursuing a “tortuous balancing act, designed to appease both sides of the debate”. “By this means,” writes Saunders, “the party hoped to refocus attention away from the merits of the Community and on to the right of Scotland to make its own decisions.”

That assessment might sound familiar, for it also characterises the SNP’s strategy following the 2016 referendum. The First Minister abandoned a full-blooded argument for continuing membership of the European Union early on and instead settled upon another flimsily-clad compromise – membership of the Single Market. Much more prominent has been a simpler argument about sovereignty, that whatever happens Scotland ought to decide.

It looks, however, as if the SNP has repeated an historical error. In 1975, it viewed the referendum as an opportunity to build electoral support – it distributed membership forms with its anti-Market campaign material – while in 2016 Nicola Sturgeon believed a differential vote (ie Scotland “Remain”/England “Leave) would boost support for independence.

On both occasions, this analysis proved faulty. When in 1975 a majority of Scots actually voted “Yes” to continuing membership of the Single Market – contrary to earlier polling – the SNP was shocked to discover, as Saunders writes, not only “how badly they had misread the public mood” but also “how little they had been able to shape it”.

The pollster Sir John Curtice made a similar point in a recent blog for the “UK in a Changing Europe” website, observing that rather than Scotland’s 62 per cent “Remain” vote “creating a bandwagon in favour of independence”, Brexit had instead exposed “a fissure in the nationalist movement that Nicola Sturgeon has struggled to straddle”.

That “fissure” has long been present, not only during the 1975 Common Market referendum but in the late 1980s when the SNP staged an audacious about-turn on a major plank of policy (much like Nato in 2012), committing itself to the oxymoronic goal of “independence in Europe”. In 1990/91, 300 SNP members, including the former MP Donald Stewart, signed a “Sovereignty 90” charter which repudiated the party’s new pro-European stance.

What the 2016 referendum did was significantly widen that once-miniscule fissure, although many Nationalists are still in denial about this. As Sir John also points out, the 2016 Scottish Social Attitudes Survey found that 37-38 per cent of those who voted SNP in that year’s Holyrood election went on to support Leave. At the following year’s general election, many of those deserting the SNP were also Leavers.

This also explains why the SNP is currently sustaining the world’s most boring constitutional crisis, negotiations over Clause 11 of the European Withdrawal Bill. Rather than the Scottish Government trying to obstruct Brexit, it’s instead sought refuge in its “sovereignty” comfort zone. As the hyperbolic Ian Blackford claimed on Wednesday, the Prime Minister wants to oversee “the demolition of the devolved settlements”.

Recently, the First Minister suggested the compromise of a “sunset clause”, but to the UK Government – more preoccupied with a challenging legislative programme than grabbing powers from Scotland and Wales – that simply means a series of further rows with the Scottish Government, the “common frameworks” under dispute having to appear on the face of 24 sector-specific Brexit bills.

As usual, it begs the question – to what end? As the SNP has discovered to its cost, Brexit didn’t boost independence, so it’s now hoping Scots will rise up against an (exaggerated) assault on the devolution settlement. Good luck with that.